1. FIELD OF THE INVENTION
The present invention relates to a thermal transfer recording apparatus for forming images on an image recording paper by feeding an ink film and an image recording paper between a platen and an print head and transferring the ink from said ink film onto the image recording paper.
2. DESCRIPTION OF THE RELATED ART
The ink films used by thermal transfer recording apparatus include fusion type films wherein a print head thermally fuses the ink of an ink film so as to adhere said ink onto an image recording paper, sublimation type films wherein a print head sublimates the ink of an ink film so as to adhere said ink onto an image recording paper, and the like. U.S. Pat. No. 4,876,235 discloses a sublimation type ink film wherein the ink of an ink and the image recording paper is prevented via the presence of spacer beads on either said ink film or said image recording paper.
In thermal transfer recording apparatus using conventional thermal sublimation type ink film, a large pressure is applied to the image recording paper and the ink film via a print head and platen.
However, conventional thermal transfer recording apparatus using sublimation type ink film typically produce white-spot phenomenon called voids due to surface irregularities of about 2 .mu.m on the surface of the image recording paper, and said voids are produced even when an ink of laser-induced ink sublimation type is used. The occurrence of the aforesaid voids is thought to be caused by the relatively low dye transfer efficiency of the concave portions of the aforesaid surface irregularities of the image recording paper due to gaps between said concavities and the ink film compared with the relatively high dye transfer efficiency of the convex portions of said surface irregularities.
Furthermore, since the dye layer of the ink film contains binding agents and the like in addition to the dye, said binding agents and the like are transferred to the image recording paper as impurities which may cause image irregularities. Accordingly, a major technical problem today is preventing the production of the aforementioned voids as well as preventing the occurrence of irregularities in an image caused by the transfer of the aforesaid impurities so as to allow the reproduction of high quality images on an image recording paper.
Further, transfer efficiency could be improved if only the light energy of the laser beam used to expose the ink film to effect sublimation of the ink could be minimized. The present inventors conducted various studies to achieve improved transfer efficiency, and have determined that heretofore the ink film is fed along the feed guide surface of the print head in a state of contact therewith so that the thermal energy generated by photothermal conversion in the exposure of film is adsorbed by the print head. Heretofore, the adsorbed excess energy has unavoidably augmented laser intensity.